collisions in full-duplex ethernet

[tcherkon]

I've read a confusing question in switching exam. Here it is:

17. Which of the following are true of full-duplex ethernet?

a. There is a significant performance increase over half-duplex ethernet

b. More collisions

c. If one host is transmitting, the other must wait for it to finish

d. No collisions

e. Clients must have a full-duplex compatible ethernet card

Answers are: A,E

This seems right, but why D isn't true?

Thank you

[wynneit]

Cant think why D isnt true except when the settings are mismatched and you have one device in full duplex the other in half duplex ie if auto negotiation has failed.

[rdrummond]

This question would have confused me as well.

The only thing I can think of is during the auto-negotiation the devices use collisions to detect the correct settings.

Bobby

[ptrigueira]

Hi guys,

full-duplex ethernet, is jusr about using both uplink and donwlink for traffix. So, in full-duplex you tx and rx at the same time. If you use full-duplex in a shared media like a hub, you will FOR SURE have collisions....

pt

[glen.grant]

"D" would normally be true but then again Cisco tests are very vague in a lot of their questioning and you end up guessing just what are they looking for .

[o.hassairi]

if 2 PC r sending and receiving data in full-duplex mode then there is no collisions between these 2 PC. but if another PC is attempting to send data at the same time to one PC, is there possibility to have collisions?

[lgijssel]

No, there is no such possibility.

The Full Duplex circuit is between the SWITCH and the endstation. All traffic to other hosts is handled (queued) by the buffers in the switch.

[lgijssel]

I remember that I had this question as well, and I assume that I filled in A,D,E as well. There are quite some questions like this in any exam I took (6 of them in 2002), presumably to prevent anyone from scoring 100%.

[fbarreras]

Found an interesting comment in CCNA 640-607 certification guide on page 156. Says " If only one device is connected to each port on a switch, no collisions can occur." Take the implication and run with it.